Introduction

Have you ever wondered about why highways are designed as they are in your city every time you hit the road? Whether you enjoy the convenience brought by the highways or hate the frustration caused by congestion, our ordinary life is deeply related and directly impacted by highway designs in one way or another. In this study, we will examine the current highway systems in Oakland, California and explore how smart highway planning can improve your daily commute as well as the well-being of the city.

Context

We will conduct this study using the Ian McHarg approach, by overlaying maps of different factors using three tones of shading to indicate areas of greatest value or cost before overlaying the transparencies to find the best location for things. We will carefully examine the highway system in Oakland by looking at physiographic, natural, and social factors in the study area.

Physiographic Factors

The first group of factors which we will be looking at will be the physiographic factors that might bring potential obstructions to the construction of highways from an engineering perspective.

Slope: The slope of the study area is divided into three groups: Area with slope less than 5 degrees, area with slope from 5 to 10 degrees, and area with slope over 10 degrees. The higher the slope degree, the higher potential obstruction level and the cost of highway construction.
Seismic Zone: The seismic zones indicate areas that are prone to higher earthquake hazards and are defined into three areas based on their proximity to the Hayward fault lines: area within 1000 feet from the fault line being the most dangerous, 1000 to 3000 feet from the fault line being medium dangerous, and the rest of the study area being the least dangerous.
Geology: Geology in this context refers to the level of obstruction of bedrock in the study area. It is defined by different bedrock types as less, medium, and most obstructive. The more obstructive it is, the higher the cost for highway construction.
Surface Drainage: This factor defines where surface water or drainage channel exists. These areas are usually avoided during highway construction to stay away from extra engineering construction which requires more cost. Typically, waterbodies are the most obstructive followed by drainage channels, then areas without surface drainage.
Soil Drainage: Soil drainage measures the internal capability of soil to drain water in a certain area. Areas with poor drainage such as marshes, swamps, beach and willow groves are most obstructive and costly for highway construction while areas with high water table flows tend to be more suitable for highway construction.
Flood Zone: Flood zone is categorized into 100-year flood zone, 500-year flood zone, and no flood hazard, with 100-year flood zone being the most obstructive for highway construction for it is the most prone to flood hazard when big flood hits.

Now if we generate a map for each physiographic factors listed above, adjust the transparency, and then place them on top of each other, we will get this highway construction obstruction map of Oakland shown below.

All of the physiographic factors we have analyzed above are mapped using the same color with different opacity levels, therefore areas in white and have lighter color means there are either no or little overlaps between these factors. And the denser the colors are on this map, the harder it is to construct highways in or around the area.

Most of the physiographic cost in Oakland, California is located in southeastern side of the city closer to the fault line. There are also some physiographic costly areas on the west side of the city near the border. The layer that contributes most to the physiographic cost map is the seismic zone.

Although physiographic factors are crucial aspects that we need to consider, they are not the only factors that we need to take into account when we think about constructing highways. The existing natural resources and environmental amenities in the areas are just as significant in this age of climate change and global warning.

Natural Factors

This second group of factors which we will be examining will be the existing natural factors in an area. The more natural resources and elements in the area, the higher the value of the area, the more we want to avoid when constructing highways.

Water Value: The water value is defined by how water resources are distributed in the area. Surface water such as streams and water body give an area the highest water value followed by auriferous areas with medium water value, then area with less or no water value.
Vegetation Value: The vegetation value for each area is evaluated by their vegetation settings. Areas with well-grown forest would have the highest vegetation value while areas with grassland, scrub, and lower quality forests will have lower value, and the rest have less or no vegetation value.
Endangered Animals: This factor is delineated by the habitats of endangered animals within the study area. A high wildlife value is assigned to the areas within the habitat boundaries while the rest of the areas have little to no wildlife value.

Let’s do the same thing we did for the physiographic factors again here and combine all natural factors together to generate another construction obstruction map of Oakland.

Most of the natural values in Oakland can be spotted on the east side of the city where the forest area takes place. There are also some water value areas near the middle of the city but relatively smaller. The layer that contributes most to the natural factor map is vegetation.

However, plants and animals are not the only species we are sharing space with. Oakland is a city developed by humans after all. Therefore, the last set of factors we need to take into consideration when implementing highways will be social factors.

Social Factors

The final group of factors we will analyze today will be social factors within areas of the city of Oakland. Construction of highways will inevitably reduce the social value of the areas, so avoiding high social value areas should be our goal or priority in order to minimize the cost to purchase land and preserve community value.

Property Value: This factor is defined by the total property value of each census block group evaluated by professional assessors.
Recreational Value: Recreational value is defined by the presence of parks and other recreational sites in an area. Area that contains a park is given the most recreational value as parks provide both natural and social recreational opportunities followed by other recreational sites. Area with no recreational sites has no recreational value.
Historic Sites: These areas should be preserved for the historical, cultural, and traditional value of the city and therefore should be avoided at all costs when constructing highways.
Institutional Values: Governmental buildings and schools are given the highest institutional value. Areas that contain churches are considered medium institutional value, and the rest have no institutional value.

For one last time we will combine all social factors into one map to generate our last factors-driven highway construction obstruction map of the city of Oakland before we create our final map to analyze the land suitability for highway development for the entire study area.

The social values are distributed relatively evenly within the border of the city of Oakland, but most areas of social values can be found in the east side of the city. The layer that contributes most to the social factor map is the property value layer.

Results

Unlike Ian McHarg who relied on hard copy transparent Myra sheets to map out physiographical, natural, and social factors in different shades of grays, we are going to lay these three digital maps of geospatial data on top of each other to find out which areas are most vulnerable to highway or other infrastructural implementation as well as figuring out which layer contribute most to the cost/value of the composite map.

Now we let’s bring in the highways.

Conclusion

Some freeways in Oakland that were built on appropriate locations include I80, State Hwy 123, Moraga, and State Hwy 61. These freeways are built in suitable locations because they are either far away from social and natural value sites or were built in the least costly areas that are less obstructive. Some freeways in Oakland that were built on inappropriate locations include State Hwy 13, Mt, I 580, and State Hwy 77. These freeways are not built on suitable locations because they are too close to social and natural value sites and were built on the costliest areas that are more obstructive.

References

Data Source: LA5582/3581 Class Geodatabase 2021

A McHarg Approach to Sustainable Highway Planning

Ray Ma

9/24/2024